Process of drying.



G. H. MAY 6: W. M. GROSVENOR. PROCESS OF DRYING. APPLICATION FILED AUG. 17, 1909.

2 SHEETS-SHEET 1. l\ m 3 3 7/1 ZZWM V XQWWWWWWW Patented Oct. 14, 1913.

G. H. MAY & W. M. GROSVENOR.

PROCESS OF DRYING.

APPLICATION FILED AUG.17, 1909.

1,075,586.- Patented 001.14, 1913.

2 SHEETS-SHEET 2.

Q. ail/W W ingxnedium before it srarns rarnnr orrroa GEGBGE'H. MAY, E NEWBURGH, NEW'YORK', AND M. G-ROSVENOBI, 0F

' GBAN'DWOOD, NEW JERSEY.

PROCESS OF 'DEYING.

Specification of Letters Patent. Paflbgntlgd (M313, 14,1913.

Application fll'ed Augu st 17, 1909.: Serial no. mazes;

To all whom it'mag' concern:

Be it known that-we, GEORGEH. 'lliAY and WIILLIAM 'MQ GROSVENOR, citizens of the United" States, and residents, respectively, ofNewburgh, Orange county, New York, and Grahtwood,l3ergencou1ity, New Jersey;

have invented a certain newand useful Im-f proved Process of Drying; of which'the fol= low'ing-is 'a specification.

The invention relates to an improved; process of preparing" and drying materials which areco ated with water-proofing or othersubstances applied in the form of a solution, such, for example, aswaterproof paper or similar material.

The objects'of the invention are to dry th'material in a uniformand' efficientm'an ner, and'in such a way as top'roduce upon the material a smooth and uniform and homogeneous coatingwhich will be tough and durable and continuous, and free from cracksorholes or other imperfections; also to prevent a too rapidfdrying of the applied coating as a result of'which the'quality and durability of the coating will" be improved; also to recover the solvent employed in the: preparation of the coating so that this solventmay be usedover and over againfdr the same purpose {and generally to provide a method of drying which. will be economical and, at the-same time; produce a superior quality of finished material.

The'inventidn consists, first, in the process ofpreparing and drying materials coated with substances in solution -by first dryingthe material, then'coating it with the sub-' stance in'solution, then subjecting the coated material to a currentof air or other suitable drying medium ina closed chamber, then causing-the dryingmedium to flow througha closed condensing chamber, and then back into the drying chamber, condensing the solvent in the condensing chamber, and drawing- 05 the condensed solvent therefrom, and re-heating the drying medium heforeit" again comes into contact with the material, to the desired teinperature.

The invention also consists in'coolingthe drying medium in the condensingchamber to such'a point as to condense a part only of the solvent so that the dr'yingmedium when it flows'from the condensing chamher is partly saturated withthe solvent, and in then re-heatingthis partly saturated drya ain comes into con act with"tlie material, to a temperature a little below the boiling point;

The invention als'o'consist's in moving the material through the drying chamber at a suitable rate of speed relatively to the character of the coating" and of the material" to produce'a thorough drying of' the same before it passes out of the dr ing chamber.

The invention also consists in electrically grounding the parts of the mechanism with which the material comes into moving contact.

The invention also consists in applying successive coats to the material while it moves in reverse directions through the drying chamber so as to spread the. successive coa tingsin alternately opposite directions as a result of which imperfections in the goods are covered up. 1

The'invention also consists of other steps and features hereinafter described and claimed. Y

In the accompanying drawings an apparatusis shown'which is particularly adapted for 'carryin out this improved process, althoughother form's ofappa'ratus may be employed for this purpose.

In the edrawings; Figure 1 is a vertical longitudinal view of'the apparatus showing both ends thereof, the middle portion being broken away; and Fig. 2 is a vertical cross-sectional view through the middle of the ap aratus.

Similar numbers indicate corresponding parts in the 'two figures.

Referring to the drawings, 1 is a closed drying chamber which may be made of any suitable form and size. It is provided with walls 2, 2 of any suitable material. These walls are constructed so as to be substantially impervious to the gases developed in theapparatus, and so as not to be affected by the temperatures employed therein and so as to be substantially fireproof. These walls are preferably provided witha metal lining made of 'sultable material. This material should be of su'cha natureas not to be acted upon by the vapors or gases which are produced in the apparatus.

a is an upper wall or covering made of thincl'oth or webbing which can be easily torn so as not to confine the gases in case of such explosions as may occur with the mixture of gases present in the apparatus.

5, 5 are bearing surfaces made of metal,

preferably of copper plate, upon which or over which the material moves. These bearing surfaces are supported in any suitable manner, as illustrated in the drawings. They are grounded electrically. by electrical conductors arranged in any suitable manner. For example, 6 is a wire connecting the bearing piece 5 with the metal lining 3 of the drying chamber, and 7 is a wire connecting'th' metal lining with the heating pipes 8 placed at the -'lower part of the drying chamber, or in any other suitable location. 9, 9 are bafile plates extending throughout the length of this drying chamber and projecting from the sides of the chamber toward the middle thereof in the manner clearly shown in Fig. 2. baffle plates cause the ascending current of air to pass to the middle of the chamber and then underneath the material to the edges thereof, and then across the top of the material to the middle thereof, and then upwardly to the top of the drying chamber.

10 represents the material which is being dried.

11 is the condensing chamber which is separated from the drying chamber by the wall 12, and which is connected with the drying chamber at the top and bottom, as clearly shown in'Fig. 2, to permit of a continued circulation of the drying medium up through the drying chamber, then into the .top of the condensing chamber, and then down through the condensing chamber, and then into the bottom of the drying chamber where itis re-heated. The condensing chamber is provided with a condensing coil 13 through which cold water, orother refrigerating fiuid, may be passed so as to maintain a suitable'temperature in thecon- 22. The pipe 28 is provided with a'valve densing chamber.

14: .is a trough or receptacle to receive or catch the condensed solvent, or solvent and water, which is condensed out of the drying medium. The coil 13 is extended down to the lowest-point of the trough 14 so as 16 is a by-pass in the condensing chamber to permit the drying medium to escape past receptacle 14. V

17 'is a hinged door forming one side of the condensing chamber, by means of which :ready access can be had to the condensing chamber and the condensing pipes. Y

18 is the supply pipe of the heating coil, and 19 is the return pipe of the same.

20 is a chamber for inclosing the coating These device. The walls of this chamber are made substantially tight 'so as to prevent, so far as possible, the vapor or solvent in the drying chamber from escaping from the apparatus.

21, 21 are movable hinged covers in the upper wall of the chamber 20, preferably provided with panes of glass through which the operation of the coatingand spreading devices can be easily observed, and b means of which ready access can be had to these devices. e I

22 is a spreading device or knife adapted to slide up and down in hearings in the side walls of the chamber 20 as shown.

This knife is preferably made of metal, and

suitably grounded by connecting it electrically with the metal frame of the machine as by the wire 23. Any other suitable form.

cally as by the contact brushes '25 which i may be connected in any suitable manner with the metal lining of the apparatus.

26, 26 are pieces made of some spring material between which the material to be dried passes into the chamber 20. ,These spring pieces form a tight joint at the-place where the material passes into the chamber 20 and so prevent any substantial leakage of vapor or solvent from the apparatus. If the pieces 26 are made of metal they should be suitably grounded.

The coating compos 'ion is held in any suitable reservoir such as the tank 27, which is connected by a pipe 28 with a funnel 29 extending through an opening in the hinged cover 21 at a point outside of the knife 30, and in this manner the coating composition can be fed at any rate desired into the chamber 20 on to the material in front of the spreading or coating device.

In Fig. 1, 31 represents a' quantity of "coating composition which has been fed on to the material. The chamber 20 is provided with. a recess or depression formed bythe Wall of the chamber and adapted to receive the drip tank 33 which is placed' immediately below the coating device so as to receive or catch any surplus of the coating composition which may drop down from the material. When the tank '33 is full it can be withdrawn and emptied-in any suitable manner. Each end of the machine is pro- .vided with a chamber 20 such as already described, with all the parts from 21 to 33 inclusive. The opening for the admission of the material in the chamber 20 at one end of the machine, is on the same level as the opening for the discharge or admission of the material in the chamber 20 at the other end of the machine. Each endof the Lora-ass device is also provided with suitable driving, holding and tension devices. Any suitable devices may be employed for this purpose. In the form of apparatus illustrated, 34 is a roller which acts as a receiving roller when its end of the machine is used as the discharge end, and as the supply roller when its end of the machine is used as the supply end. This roller is slipped onto a m square shaft 35 mounted in suitable hearings in the frame of the machine. 36 is a driving roller or drum, and 87 is an intermediate roller. The driving roller may be driven by any suitable means. The particular form 35 of these driving, holding and tension devices forms no part of the present invention, as any suitable apparatus may be employed for this purpose.

No claim is made in this present apparago tus for the machine illustrated in the drawings, as this machine is described and claimed in the co-pending application of George H. May and William M. Grosvenor, Serial No. 485,401, filed on March 24, 1909. The machine is so constructed that the material may be passed through the machine in one direction, being coated with composition as it passes through the chamber 20, and being dried on its way through the drying 3o chamber, and it may then be passed back through the machine in the opposite direction for an additional coating to be applied to the material, or'it may only be subjected, upon being returned through the machine, to further drying if it is nec%sa'ry.

The improved method is carried out in this apparatus in the following ma ner, assuming that the coating substance to be applied to thematerial is made of ceresin 40 dissolved in benzol: The coating solution is placed in the tank 27 and is fed through the pipe 28 onto the top of the material in front of the coating or spreading knife 22,

as illustrated at the left hand end of Fig; 1. The material 10 is passed through the apparatus from left to right, as shown in this figure, and the coating composition is spread evenly and uniformly over the upper surface of the same by the device 22. The material thus coated is passed through the drying chamber 1 at such speed as may be suitable, relatively to the thickness and character of the coating. The air in the drying chamber is heated by the heating coil 8 to a temperature of about 140 Fahrenheit. The heated air rises by operation of gravity through the chamber 1 and is deflected by the baffle plates 9 and brought into contact with the material to be dried throughout the length of the drying chamber, and thus heats the material and causes the evaporation of the benzol contained in the coating composition, and also of any water that there may be in the material, or of a substantial part of the benzol and renheit.

water. The drying medium then flows into the upper part of the closed condensing chamber 11, and is brought into contact with the cooling coils 13, and is thereby cooled, and as a result of this substantially all of the water is condensed out of the air, and

a considerable portion of the solvent is also condensed.

The temperature of the condensing chamber is maintained at about 110 degrees Fah- The result of this is that only a part of the benzol is condensed, while substantially all of the water is condensed. The condensed benzol and water flow down into the receptacle 14 where they are further cooled to prevent evaporation and are drawn off through the pipe 15, and are thus recovered, and the benzol may be again used for preparing the coating composition. The drying medium flows away from the con- 35 densing coils through the by-pass 16 into the lower part of the condensing chamber,

and then flows back into the lowenend of the drawing chamber underneath the heating coils. When thedrying medium passes away from the condensing coils 13 it is substantially free from water, but is partly saturated with the benzol. .By thus regulating the amount or portion of the solvent which is condensed, it is possible to avoid the formation or use of highly explosive mixtures, thereby securing additional safety "and economy. The drying medium passes upwardly through the drying chamber, and

is re-heated by contact with the heating -coils 8 to a temperature of about 140 degrees Fahrenheit. It is then brought into contact again with the material 10 and causes a further evaporation and removal of solvent and water from the said material. By reason of the fact that the drying medium when it is brought into contact with the material is partially saturated with solvent, the

evolution or evaporation of the solvent from the material is less drastic and abrupt, and 10 I the drying is more uniform. As a result of this the film or layer of coating substance is less likely to be ruptured, and the coating itself, when finally dried, is more uniform in character and of a smoother surface, and with many substances is also lessbrittle. The drying medium then flows to the upper part of the condensing chamber and down through the condensing chamber as before, asa result of-which substantially all the water which it carries is condensed and a part of the solvent, as already explained. This operation is carriedon continuously, the material being moved through the drying chamber at such a rate of speed that it will be thoroughly dried before it leaves the discharge end of the apparatus, and receiving other coats as required by reverse passage through the apparatus; or the material may be partly dried in its first passage through the apparatus, and may be'passed back through the same as many times as may be necessary to thoroughly complete the drying operation. The drying chamber, and the two connected chambers 20, 20 and the condensing chamber, are all closed so as to form a closed circuit, and they are made as tight as possible so as to prevent any escape or leakage of the solvent-bearing vapors. When successive coats are applied to the material it will be observed that the second coat is appliedto, or spread upon,-

the material in a direction the reverse of that in which the preceding coat was applied to or spread upon the material; and this is done without disconnecting the material from its actuating mechanism. As a result of this, any imperfections which may occur in the first coat are filled up or covered up by the application of the second coat.

As a result of employing the upper wall 4 made of thin cloth or webbing as described above, the drying medium can be circulated at atmospheric pressure by the action of gravity free from the influence of the outside pressure or from outside disturbances of any nature, and yet provision is made for the escape of a portion of the drying medium in case of any substantial increase of internal pressure caused, for example, by an explosion. The action of the drying medium is made independent of the conditions existing outside of the apparatus, as the outside atmosphere has no access to the apparatus, but, at the same time, should any explosion occur, a vent is provided for the gases formed thereby, as a result of which the apparatus would not be injured, or the injury would be reduced to a minimum. I

When the complete invention is employed the material is dried by any suitable means before it is introduced into the apparatus, so that any moisture or water contained therein will be substantially eliminated before the coating substance is applied to the material. As a result of this the amount of water which is evaporatediin the apparatus and condensed in the condenser, is reduced to a minimum, and the liquid drawn off from the condenser contains a smaller proportion of water.

It willbe apparent that other coating substances may be used in place of ceresin, and that other organic solvents maybe employed instead of benzol and solvents such as carbon tetrachlorid (C61,) are regarded as organic solvents. Also that when in this specification substance in solution is used, it is not intended that all of the substance must be in solution,only suflicient of it 4 need be dissolved to soften the substance and render it more or less plastic.

The invention secures marked advantages, 4

some of which are as follows: The material is dried by a medium already partly saturated with the solvent, whichmakes the drying less rapid or abrupt, and produces a better quality of coating and a more durable one. The solvent, which is generally expensive, is almost entirely recovered and saved so that it may be used over and over again, thus producing very substantial economy in the operation. The fact that the drying medium is moist with solvent when it enters the drying chamber and comes int-o contact with the heating coils, enables it to transmit heat to the fabrlc more quickly than if the medium were perfectly dry. The specific heat of the moist medium is greater than the specific heat of the mediumlwhen dry. The drying is also accomplished with a minimum expenditure of heat, as excessive temperatures in the drying chamberare purposely avoided. The

.drying medium may be maintained in a practically non-explosive mixture; the possibility of ignition is further reduced by avoiding stray electrical discharges; and, finally, should" ignition occur, an unrestrained and therefore harmless explosion is permitted.

The method is simple and easily carried on.

What is claimed as new, is as follows:

The improved method of drying coated sheets and the like carrying volatile organic solvents, which consists in causing the sheet to move through a drying medium during the drying operation, simultaneously causing the drying medium to circulate about the sheets, the drying medium being partially saturated with the organic solvent vapors to be removed before it comes into contact with the sheet, and heated to a temperature below the boiling point of the solvent, the temperature and'saturation being so adjusted relatively to one another so that premature surface drying of the coating 1s prevented, and whereby the movement of the mediumcauses the .body of the sheet and coat-ing to become gradually heated and the vapors to be driven off gradually to prevent blistering, bubbles and pinholes.

In testimony whereof, we have signed our names to this specification, in the presence of two subscribing witnesses.

GEORGE H. MAY. ILLIAM M. GROSVENOR. l/Vitnesses T. E. RAFTERY, EDWIN Snonn.

It is hereby certified that in Letters Patent No. 1,075,586, granted October 14, 1913, upon the application of George H. May, of Newburgh, New York, and William M. Grosvenor, of Grantwood, New Jersey, for an improvement in Processes of Drying, an error appears in the printed specification requiring correction as follows: Page 3, iine 89, for the Word drawing read drying,- and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent )fice.

Signed and sealed this 9th day of December, A. 1)., 1913.

SEAL J. r. NEWToN,

Acting Commissioner of Patents. 

